roman tub valve HELP !!!.. I need some sound advice

I recently had my master bathroom remodeled including new travertine on the floors, shower, shower ceiling, new cabinets, counter tops, stone mosiac sinks.. AND roman tub surround.... The installers agreed that the tub framing and the old ceraimic tile were 100% sound enough to tile over (I understand this is commonm practice). the tub backerboard is 100% mudded (no hardiboard as te home was built in the early to mid 1980's) I removed the old valves by carefully chipping away the cement (the valves were installed into the Plywood and then mudded over, I had no choice.

Regardless the tile guys went ahead and installed the new stone over the existing tile on the deck of the roman tub...

HERE is the question in a nut shell..........

The deck is thick now... the new price pfister roman tub hardware has to be retro fitted into the new area.

Sorry is this is a little confusing but how do I do this .... not sure how to mount the valves at this point... forstner (sp) to open up the bottom? OR valve extenders.... I will take some photos as soon as possible.... WHAT do you folks need to see in order to help out ???????

I've had to buy stainless plate with rounded edges, make hole in deck big enough attach plate to ceremic and drill holes for faucet. Home made base plate, some faucets come with them. I don't know if you could buy one ready made. I have a guy that makes them when I need them. He welds studs to the bottom and cuts the holes for the faucet. I don't need screws you can see that way to attach it.

If you had durarock underlayment you could just remove the plywood from underneath, but I don't think that will work with mudbed. You could try.